1. Field of the Invention
This invention relates to an automotive suspension control system including a suspension position sensor.
2. Disclosure Information
Automotive suspensions employing adjustable suspension units typically utilize one or more sensors for detecting the position of one or more portions of the suspension with respect to either another part of the suspension itself or another part of the chassis of the vehicle. In the case of vehicles using load leveling or air or hydropneumatic suspension systems, it is necessary to know the ride height of the vehicle in order to determine whether correction of the ride height is required. In the event, for example, that the ride height is less than prescribed limits, as determined by the height sensor, an adjustable suspension unit may be given the command to increase the ride height. Conversely, in the event that the ride height exceeds the prescribed limits, the adjustable suspension unit may be given the command to lower, or decrease, the ride height.
Vehicular height sensors are useful not only with ride height adjusting systems but also as transducers for use with adjustable suspension dampers. A sensor according to the present invention is useful for providing not only suspension motion information but also ride height information for use with a vehicle leveling system or an air or hydropneumatic adjustable suspension or other type of adjustable suspension system.
U.S. Pat. No. 4,105,216 discloses a motor vehicle level control circuit in which a pair of optical detectors interacts with a rotary shutter device to produce a first logic signal pair when the vehicle's ride height is in a trim region, and second and third logic signal pairs when the vehicle's ride height is either high or low but out of the trim region. The system of the '216 patent has the capability of producing only three logic signal pairs with the two detector devices. A sensor according to the present invention, however, will have the capability to produce, with only two detector devices, four logic signal pairs defining a total of seven ride height states which correspond to seven states of the height sensor.
U.S. Pat. No. 4,453,725 discloses a rotary height sensor using a bifurcated shutter and three optical devices in order to produce a sensor having resolution of vehicle position into five possible levels. Note that the system of the '725 patent requires three optical devices and corresponding logic circuits in order to produce resolution to five states.
U.S. Pat. No. 4,433,849 discloses a vehicle leveling system having two reference vehicle height positions requiring separate detectors for each reference vehicle ride height position.
A variety of sensing techniques have been employed with vehicular height sensors. These include, without limitation, electro-optical devices, linear variable differential transformers, and Hall Effect devices. Examples of the latter are disclosed in U.S. Pat. Nos. 3,473,109; 4,107,604; 4,204,158; and 4,555,120. None of the sensors disclosed in these patents has the capability of providing multiple position signals including interspersed congruent and incongruent logic states from a plurality of detectors.
It is an object of the present invention to provide a height sensor capable of accommodating a plurality of reference vehicle ride height positions with a single height sensor containing only two detectors.
It is another object of the present invention to provide a height sensor and suspension control system which may be employed to produce a plurality of controlled ride heights.
It is another object of the present invention to provide a method for assuring that a parked vehicle does not become lodged upon an obstruction situated under the vehicle.
It is another object of the present invention to provide a suspension position sensor which furnishes more information than prior art sensors having the a similar level of detection capability.
Other objects, features and advantages of the present invention will become apparent to the reader.